Re: [Xen-devel] SMP boot time-out with PCI Passthrough

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 02/09/2009 14:29, "Fredin, Jerry" <Jerry.Fredin@xxxxxxx> wrote:

> I¹ve tracked it down so far to the ept_change_entry_emt_with_range function
> taking the majority of the time.  Since this function is not executed if
> has_arch_pdevs(v->domain) returns zero, it explains why it only happens with a
> passthrough device.
>  
> Is the .8 seconds per GB an expected execution time or is this a known problem
> I missed in my searches?

I doubt the function was implemented with performance in mind at all. The
fact it has cost proportional to memory allocated to guest is not great of
course. You could work around this quite satisfactorily I'm sure, by
configuring hap=0 in your domain config file. Shadow page tables work pretty
well, and won't use this costly function at all.

 -- Keir





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